Electronic organ employing a reverberation unit with variable decay time

ABSTRACT

An electronic organ in which all of the tones generated are applied through an artificial reverberation unit to the output speakers. The reverberation unit includes a pair of coiled springs with a coupling section between two portions of each spring. The reverberation or decay time is varied by an adhesively coated wire which is controllably brought just to rest on the coupling section so as to adhesively grasp the section. Since all of the signal is passed through the springs, the tone generators may be designed to compensate for both the poor frequency and the poor tonal characteristics of the springs, whereby exceedingly low frequency tones can be transmitted through the reverberation unit and have their reverberation time controlled and the metallic sound usually associated with reverberation units obviated.

United States Patent [72] Inventor Leonard W. Pavia 460 Columbia Turnpike, Florham Park, NJ. 07932 [21] Appl. No. 822,468 [22] Filed May 7, 1969 [4S] Patented Feb. 16, 1971 [54] ELECTRONIC ORGAN EMPLOYING A REVERBERATION UNIT WITH VARIABLE DECAY TIME 12 Claims, 5 Drawing Figs.

[52] US. CL... 84/1.24; 333/30, 333/71 [51] Int. Cl Gl0h 1/02 [50] Field ot'Search 84/1.24, 1.01, 1.05, 1.06(R 179/1 (M); 84/1.24 (R) [56] References Cited UNITED STATES PATENTS 2,230,836 2/1941 Hammond 179/1(M) KEYBOARD liER/AL "0.545s". l

2,949,805 8/1960 Hammond Primary Examiner- Milton 0. Hirshfield Assistant Examiner-Stanley J. Witkowski Attorney.lames W. Falk ABSTRACT: An electronic organ in which all of the tones generated are applied through an artificial reverberation unit to the output speakers. The reverberation unit includes a pair of coiled springs with a coupling section between two portions of each spring. The reverberation or decay time is varied by an adhesively coated wire which is controllably brought just to rest on the coupling section so as to adhesively grasp the section. Since all of the signal is passed through the springs, the tone generators may be designed to compensate for both the poor frequency and the poor tonal characteristics of the springs, whereby exceedingly low frequency tones can be transmitted through the reverberation unit and have their reverberation time controlled and the metallic sound usually associated with reverberation units obviated.

S ELL CONTROL I AMPLIFIERS ELECTRONIC ORGAN EMPLOYING A nEvERBEnATioN UNIT WITH VARIABLE'DECAY TIME BACKGROUND OF THE INVENTION In electronic musical instruments it is often desirable to introduce reverberation effects. This is particularly true of electronic organs. One known wayof introducing such reverbera- 'tion, as in Hammond US. Pat. No. 2,230,836, Feb. 4, 1941, is to cause a coiled spring or springs to vibrate in response to the electrical signals representing the musical tones. The springs may be vibrated in either the torsional or compressional A problem has existed in enabling changes in the reverberal tion time of such systems. Often'in playing an instrument, such as an electronic organ, it is desired to change the reverberation or decay time of the sound for different musical pieces. A number of unsatisfactory solutions have been used; these solutions have either involved a mechanical damping of the springs or a change of the ratio of ,the signal passed through the reverberation unit and the signal applied directly to the speakers.

' The most common procedure, particularly when a reverberation unit is added to an organ, has been tovary the ratio.

'It has been customary to pass most of the signal directly from the input to the output amplifiers and speakers without passing through the reverberation unit. By ase'parate control the amount or volume of the signal passed through the reverberation unit can be adjusted. In this way the apparent reverberation period is changed as a larger or smaller portion of the total signal volume bypasses the reverberation unit. Needless to' say this technique does not truly change the reverberation 7 period even though the apparent effect on the listener is a lessening of the reverberation.

This technique has also been used because the reverberation units have poor sound characteristics, contributing a tinny or metallic sound to the final-sound applied to the speakers. Since only a small portion of the signal is applied to the reverberation units this metallic sound effect is masked.

In such systems where the signal is passed both through a reverberation unit and in bypass of it, it has not been possible to obtain satisfactory reverberation characteristics over the full frequency range that is desired for an organ. Reverberation units, because of their physical structure and mode of operation, have very poor low frequency responses and, in general, are considered to have a low frequency cutofi at about 200 cycles, which is higher than the lowest notes desired for an organ. i

Despite these basic deficiencies, however, this bypass technique has been used considerably, particularly since it can be added onto existing electronic organs. It does give an effect ofan organ reverberation and this effect can be easily varied. It is obviously a poor compromise, however, since it relies on the major portion of the signal not passing through the reverberation unit in order to mask out the inherent deficiencies of the unit and eventhen it is not effective over the full frequency range.

The other techniques utilized or proposed involve some from of mechanical damping. One. known system requires immersion of the springs in moreor less oil. Another utilizes a felt damper forced down on a portion of the springs. These arrangements change the effective'lengths of the springs or their resonant periods. These techniques also have disadvantages. Since the damping to be effective requires a considerable mechanical change in the system, as by exerting considerable force on the felt damper, the frequency response of the reverberation unit is changed, limiting both the high and low frequencies. A further difficulty has been that the damping lessens the amplitude of the signal.

In addition to prior damping techniques involving forcing an element onto thesprings,'damping has also been attempted in which the dampirig material, such as a felt. was only lightly placed on the springs so as not to bear on them with sufficient force to lessen the signal amplitude. Unfortunately this results in a scratchy sound as the springs physically move, due to the compressional or torsional action of the springs, under the damping material. The scraping of the springs against the damping material is then picked up on the springs and applied to the amplifiers and the speakers, resulting in the aforenoted scratching or scraping noises appearing in the musical tones from the speaker.

BRIEF SUMMARY OF THE INVENTION I have found that an effective reverberation unit in whichthe length of the reverberation time may be readily changed may be obtained by a different approach to the problem of changing the physical characteristics of the springs. Further my invention may be employed with several types of existing reverberation units, whether of the compressional or torsional types.

In existing torsional reverberation units it is customary to have one part of the spring wound in one direction and then have the other portion of the spring wound in the opposite direction. A flat or smooth coupling section is positioned between these two sections to couple them together. In one embodiment of my invention, my reverberation control is exercised on this flat or nonwound portion of the reverberation springs so as not to interfere with the motion of the coils of the springs.

Further, in accordance with an important aspect of my invention, all of the signal may be passed through the reverberation units with none of the signal bypassing the units directly to the speakers. I have foundthatl can, by proper scaling and voicing of the signals applied to the reverberation unit, compensate for the poor low frequency characteristics of the reverberation unit itself and can also compensate forthe metallic sound priorly associated with reverberation units. Specifically l can compensate for the frequency characteristics so as to obtain excellent reverberation characteristics for signals as low as l6 cycles.

Accordingly, I can scale and voice signals so that, first, the bass componentsare exceedingly heavy, thereby compensating for the inferior frequency characteristics of the reverberation unit itself, and, so that, second, the inherent tonal handicaps of the reverberation unit are overcome. Since all of the signal is passed through the reverberation unit, in accordance with an aspect of my invention; and none of the signalin bypass of the unit, I need only be concerned with the character of the signal at the output of the reverberation unit and not at the input, except in so far as the input signal is specifically designed to give the desired output. This has not priorly been true as the signal atthe input of the reverberation unit was also the major'portion of the signal applied directly to the speakers.

Accordingly, my reverberation unit acts as a delay line over a far wider range of frequencies to give a truly pipelike effect when incorporated into an electronic organ. Further, a reverberation unit in accordance with my invention introduces a slight delay in the tonal attack duplicating the tonal attack of the pipe organ and the delay introduced by the air columns in the pipes.

My organ, incorporating a reverberation unit is accordance with my invention, has another important advantage. Priorly it has been customary to voice a pipe organ depending on the nature of the room in which it is played. If the room is relatively dead, then the organ is voiced to strengthen the lower notes andlower the treble; conversely, if the room has a good deal of inherent reverberation, then the treble is strengthened and the has lowered. With my organ however, the organ is properly voiced for any room when the tones are voiced to compensate for the characteristics of the reverberation unit. For different types of rooms only the reverberation time of the reverberation unit need be changed, but importantly the organ need not be revoiced. I

In the specific illustrative embodiment of my invention described herein my reverberation time control comprises a fine metal bar or wire having an adhesive coating on it. The adhesive bar is controlled from a remote location, as by a switch on the organ stop board. This switch actuates a solenoid so as to cause the bar to just touch the flat coupling or uncoiled section between the two portions of the springs or to remove the bar from the reverberation springs. The control bar or wire bears very lightly upon the springs os as not to decrease the volume or amplitude by impairing the vibration of the spring. At the same time, because of the adhesive nature of the coating on the wire, the control wire grips the coupling section securely so that there is no relative motion between the spring and the control wire, as would cause the priorly objectionable scraping or buzzing sound.

Accordingly, it is a feature of my invention that a reverberation time control element include an adhesive surface so as to grip the reverberation springs securely without a force bearing against the springs.

It is another feature of my invention that the reverberation time control element be actuated by mechanical or electromechanical means, such as a solenoid, so as to be readily changed, as from the face of the electronic organ.

It is a further feature of my invention that all of the sound signals can be passed through the reverberation units without a change in volume or amplitude as the reverberation time of the signal is changed.

It is still another feature of my invention that the tone generators, the voicing and filtering system, and the keying and scaling system compensate for the poor frequency and tonal characteristics of the reverberation units so that with all of the tone signals applied through the reverberation units to the speakers, very low frequency notes can be passed through the reverberation units. Accordingly, it is a feature of one aspect of my invention that the tone signals be heavily weighted at the lowest frequencies and that this voicing can be obtained through the use of a tone-generating and -keying system including conductive bus bar and selectively positioned output taps on the conductive bus bars.

DESCRIPTION OF THE DRAWING FIG. 1 is a top view of a reverberation unit illustrative of one embodiment of my invention;

FIG. 2 is a view of the coupling section between the two portions of the reverberation springs in the embodiment of FIG. 1;

FIGS. 3A and 3B are side views of the solenoid and adhesive control wire of the reverberation unit of FIG. I, in the unoper ated and operated positions, respectively; and

FIG. 4 is an idealized schematic of an electronic organ in accordance with my invention and incorporating the reverberation unit of FIG. 1.

DETAILED DESCRIPTION Turning now to the drawing, there is depicted in FIG. 1 a reverberation unit in accordance with one illustrative embodiment of my invention. As there seen the unit comprises an outer housing 8 in which floats an inner channel 10 supported from the housing as by short and relatively heavy springs 9. A mounting plate 12, which may be of wood, is secured across the side portions 11 of the housing 8, as discussed further below. Within the channel 10 are mounted a first electromechanical transducer 13 which serves as the driver for the reverberation unit and a second electromechanical transducer 14 which serves as the pickup for the unit. These transducer, which may be of any of several types known in the art, include coils 16 which are wound on a core, not shown, so as to define a magnetic circuit including the annular laminations I9; connections to the external circuit to and from the coils 16 are by means of leads l8. Positioned within the magnetic circuits thus defined are highly compliant wires, such as of beryllium copper, whose ends 20 are bent in the form of a hook. Each of these wires extends into and is supported by a tubular housing 21; further, as is known in the art, a small diameter annular permanent magnet, not shown, surrounds the end 20 of each of the wires and is positioned within the magnetic circuits of the laminations l9.

Extending between the hooks 20 are two spring elements 25 and 26 advantageously of slightly different lengths or number of turns so as to have slightly different transmission characteristics. In this specific embodiment the springs operate in a torsional mode and are each divided into two sections, the two sections being wound in opposite directions. The two sections are joined together by a coupling sleeve 28, as seen best in FIG. 2, connecting theportions 25a and 25b of the spring 25. This coupling sleeve, which has priorly been employed solely to couple two oppositely wound portions of the spring, may advantageously be used in accordance with my invention for another purpose. However, my invention is not to be considered as dependent upon such a sleeve, as depicted. In other arrangements, wherein the spring is not oppositely wound in different portions, an extended or flat single turn may be utilized for the purposes of my invention, as described further below.

As is known, even though vibrations are introduced by rotation of the books 20 of the driver transducer 13, thereby causing torsion or rotation waves to be transmitted along the springs 25 and 26, the springs may also tend to vibrate in a compression mode; by oppositely winding the two portions of the spring a net cancellation of the compressional vibrations may be obtained.

The sound or signal launched upon the springs by the driver transducer 13 travels to the pickup transducer 14 over the two springs in a few tenths of a second, the exact times being different for the two springs. The major portion of the sound energy will be reflected back from the terminating impedance at the pick up transducer 14 while only a minor portion will vibrate the magnet within the magnetic circuit of the laminations 19 causing a signal to be induced within the coil 16 of the pickup transducer 14. The portion of the signal not reflected will be absorbed within the housing 21, as by an absorbent material wire support. The reflected portion will in turn have the major portion of its energy reflected back from the input transducer and traverse the springs again to the pickup transducer 14.

The decay time of the resultant sound is thus determined by various characteristics of the reverberation unit, namely the transmission time of the springs and the proportion of the signal reflected back upon the springs at each transducer.

I have found that the'decay time of signals from a reverberation unit can be decreased without any lessening of the amplitude of the sound by restraining the action of the spring, in accordance with my invention. As can be seen in FIGS. I and 3 a solenoid 30 is mounted on the plateor board 12, by a support member 29. The solenoid 30 includes a base member 36 rigidly affixed to the support member 29; a magnet 33 within the coil of the solenoid 30 so as to be energized thereby; a lever 34 hinged at the end of the base member 36 so as to swing over and adjacent the magnet 33 when the solenoid is energized; and a return spring 35 for returning the lever 34 when the solenoid is deenergized, the support member 29 serving also as a stop to limit the return movement of the lever 34. The rod 31 is affixed to the lever 34 and moves with it, although in the opposite direction since it is on the opposite side of the pivot point. Accordingly, when the lever 34 is pulled upwards by the solenoid 30, the rod 31 moves downwards towards the reverberation springs. As best seen in FIG. 1 the rod 31 advantageously has a forked portion to allow support at two points of a thin wire member 32.

the solenoid 30 is adjusted in its mounting and in the relative positions and dimensions of the straight and forked portions of the wire 31 that the wire 32 just touches the coupling sleeve when the solenoid is energized. Because of the adhesive coating on the wire 32, the wire grips the coupling sleeve 28 without any force bearing down on the sleeve 28, as would diminish the amplitude or change the frequency response of the transmitted signal along the springs, and without the possibility of the motion of the spring causing any relative motion between the wire 32 and the sleeve 28, as would give rise to the aforenoted undesirable scraping noise.

7 in this embodiment of my invention a solenoid has been depicted as the controlling element for the adhesive coated wire 32 and the solenoid has been depicted so that the wire 32 adhesively grips the sleeve 28 when the solenoid is energized and is re'moved from the sleeve when the solenoid is not energized. ltis to be understood, of course,-that the depicted arrangement is merely exemplary and that the wire 32 could be positioned beneath the sleeve 28 or the solenoid differently mounted so that the wire would be removed from the sleeve when the solenoid is energized but would adhesively grip the sleeve when the solenoid was not energized. Similarly, a purely mechanical motion control could be utilized in place of the solenoid 30. By utilizing a single adhesive control wire 321 have readily been able to shorten the length of the reverberation time of the resultant signal from about 3 seconds in length to a second without any diminution of the amplitude or quality of sound of the signal and with all of the signal passed through the reverberation unit, as discussed below with reference to Fig. 4. However, if different reverberation or decay times are desired one may utilize a plurality of adhesive coated wires in accordance with my invention, positioned at different intervals along the springs. I

, Turning now to FIG. 4, l have there depicted in simplified schematic form an electronic organ in which my present invention may be incorporated. The advantage of my present invention in such a combination is that all of the signal may be transmitted through the reverberation unit and therefore the signals applied to the input of the reverberation unit may be a tailored, that is they may be voiced and scaled specifically to match the frequency characteristics of the reverberation unit and compensate for its odd metallic resonant quality.

As is well known, reverberation units of the type to which my invention may be applied have very poor low frequency characteristics. in prior reverberation units where the change in amplitude concomitant upon a change in reverberation time has been masked by feeding only a portion of the signal through the delay unit, it has generally been considered that reverberation below 200 cycles will not occur. In accordance with my invention, however, the signals generated by the keying system 40 are specifically voiced and scaled so as to be exceptionally heavy or strong in the lower frequencies, such as below 200 cycles. The keying system 40 is advantageously as disclosed in my copending application Ser. No. 545,987, filed Aug. 27, i966, now U.S. Pat. No. 3,463,867, issued Aug. 26, 1969. Tone generators 41, which may include the random sdund apparatus of my U.S. Pat. No. 3,405,223, Oct. 8, 1968, are connected to the electrical contacts of the individual keys of the keyboard 44. Each such contact is operable, upon depression of its key, to bear down and compress a conductive rubber bus bar 42 through which the tones are applied to the filters 43. Output taps are provided for each bus bar and are spaced along the bus bar longitudinally with respect to the key contacts so that each bus bar can be individually scaled. Specifically less longitudinal electrical resistance will be included between the key electrical contacts for the very low notes and the output taps to the filters so that the signals applied to the preamplifier 46 will be overbalanced in these lowerfrequencies.

The output of the preamplifier 46 is applied through a gate circuit 47 to the input or drive transducer 13 where the electrical signal is changed to a mechanical signal and launched upon the springs 25 and 26. The characteristic of these springs serves to reduce the predominant bass frequencycharacter of the signal so that the output signal, from pickup transducer 14, contains the bass frequencies in proper proportion and voicing to the other frequencies. This output is then applied through a second preamplifier 49 and swell control and amplifier circuits 50 to the speakers 51, which may include organ tone changers, as described in my U.S. Pats. No. 3,217,580, Nov. 16, 1965, and 3,379,275, Apr. 23, 1968, and coupled sound boxes, as described in my application Ser. No. 666,760, filed Sept. 11, 19 67.

In this way the very low frequencies have their reverberation times varied with no loss in amplitude.

As can be seen in HQ. 4 the solenoid 30 may advantageously be controlled by an obvious circuit including a voltage source 54 and a switch 55, which may be positioned on the face or console of the organ.

While a specific illustrative embodiment of my invention has been described, it is apparent that various modifications may be made by those skilled in the art, such as with respect to the type of reverberation units, the form and shape of the adhesive control wire, or the manner of providing the input signals to the reverberation unit, which signals are heavily scaled or weighted in the low frequency tones.

Iclaim:

1. An electronic musical instrument including a reverberation unit comprising means for transmitting a mechanical signal, input transducer meansfor launching said mechanical signal in response to an electrical signal, output transducer means for picking up said mechanical signal and producing an electrical signal, and changing means for changing the reverberation time of said unit, said changing means including an adhesive coated member and means for causing said adhesive coated member to contact said transmitting means so as adhesively to grip said transmitting means;

means for producing input signals for said unit including means for voicing said signals so as to compensate for the poor low frequency and sound characteristics of said reverberation unit;

means for applying all said input signals to said input transducer means; and

output means including amplifying means and speakers connected to said output transducer means.

2. An electronic musical instrument in accordance with claim wherein said transmitting means includes a coiled spring.

3. An electronic musical instrument in accordance with claim 2 wherein said coiled spring has a first and a second portion and an uncoiled section between said portions and said adhesive coated member contacts said uncoiled section.

4. An electronic musical instrument in accordance with claim 1 wherein said means for causing said adhesive coated member to contact said transmitting means includes solenoid means.

5. An electronic musical instrument in accordance with claim 4 wherein said transmitting means comprises at least one coiled spring.

6. An electronic organ comprising means for producing tone signals heavily weighted at the lowest frequencies, a reverberation unit including a coiled spring, said unit having a poor low frequency characteristic, means applying all of said tone signals to said reverberation unit, output means including speakers connected to said unit, and means for varying the reverberation time of said unit without changing the amplitude or frequency response of said tone signals applied to said unit.

7. An electronic organ in accordance with claim 6 wherein said means for varying the reverberation time includes an adhesive coated member and means for moving said adhesive coated member so as adhesively to grip said spring.

8. An electronic organ in accordance with claim 7 wherein said adhesive coated member is an adhesive coated wire and said means for moving said adhesive coated member includes a solenoid.

9. An electronic organ in accordance with claim 8 wherein said reverberation unit includes a pair of coiled springs each including a first and a second portion and a coupling section between said portions, said adhesive coated wire being positioned so as adhesively to grip said coupling sections.

10. An electronic organ comprising means for selectively generating tones including tone generators, conductive bus bars, and filters;

reverberation means for increasing the decay time of said tones;

speaker means;

means for applying all of said tones from said filter means to said reverberation meansand from said reverberation means to said speaker means; and

controllable means for varying the reverberation time of said reverberation means;

said tone generating means compensating for the frequency characteristics of said reverberation means.

11. An electronic organ in accordance with claim 10 wherein said reverberation means includes means for transmitting mechanical oscillations and said controllable means includes means for adhesively gripping said mechanical oscillation transmitting means.

12. An electronic organ in accordance with claim 11 wherein said mechanical oscillation transmitting means includes a coiled spring. 

1. An electronic musical instrument including a reverberation unit comprising means for transmitting a mechanical signal, input transducer means for launching said mechanical signal in response to an electrical signal, output transducer means for picking up said mechanical signal and producing an electrical signal, and changing means for changing the reverberation time of said unit, said changing means including an adhesive coated member and means for causing said adhesive coated member to contact said transmitting meaNs so as adhesively to grip said transmitting means; means for producing input signals for said unit including means for voicing said signals so as to compensate for the poor low frequency and sound characteristics of said reverberation unit; means for applying all said input signals to said input transducer means; and output means including amplifying means and speakers connected to said output transducer means.
 2. An electronic musical instrument in accordance with claim wherein said transmitting means includes a coiled spring.
 3. An electronic musical instrument in accordance with claim 2 wherein said coiled spring has a first and a second portion and an uncoiled section between said portions and said adhesive coated member contacts said uncoiled section.
 4. An electronic musical instrument in accordance with claim 1 wherein said means for causing said adhesive coated member to contact said transmitting means includes solenoid means.
 5. An electronic musical instrument in accordance with claim 4 wherein said transmitting means comprises at least one coiled spring.
 6. An electronic organ comprising means for producing tone signals heavily weighted at the lowest frequencies, a reverberation unit including a coiled spring, said unit having a poor low frequency characteristic, means applying all of said tone signals to said reverberation unit, output means including speakers connected to said unit, and means for varying the reverberation time of said unit without changing the amplitude or frequency response of said tone signals applied to said unit.
 7. An electronic organ in accordance with claim 6 wherein said means for varying the reverberation time includes an adhesive coated member and means for moving said adhesive coated member so as adhesively to grip said spring.
 8. An electronic organ in accordance with claim 7 wherein said adhesive coated member is an adhesive coated wire and said means for moving said adhesive coated member includes a solenoid.
 9. An electronic organ in accordance with claim 8 wherein said reverberation unit includes a pair of coiled springs each including a first and a second portion and a coupling section between said portions, said adhesive coated wire being positioned so as adhesively to grip said coupling sections.
 10. An electronic organ comprising means for selectively generating tones including tone generators, conductive bus bars, and filters; reverberation means for increasing the decay time of said tones; speaker means; means for applying all of said tones from said filter means to said reverberation means and from said reverberation means to said speaker means; and controllable means for varying the reverberation time of said reverberation means; said tone generating means compensating for the frequency characteristics of said reverberation means.
 11. An electronic organ in accordance with claim 10 wherein said reverberation means includes means for transmitting mechanical oscillations and said controllable means includes means for adhesively gripping said mechanical oscillation transmitting means.
 12. An electronic organ in accordance with claim 11 wherein said mechanical oscillation transmitting means includes a coiled spring. 